The invention described herein may be manufactured and used by or for the Government of the United States of America for government purposes without the payment of any royalties therefor.
The present invention relates in general to a safe and arm apparatus and, in particular, to a safe and arm apparatus for use in a projectile, such as a tank round.
U.S. Pat. No. 3,613,595 discloses a tail fuze that uses the air stream and mechanical mechanisms to arm a fuze in flight. U.S. Pat. No. 4,145,971 describes an electronic time delay safety and arming mechanism. The ""971 device is a stand alone electronic safe and arm apparatus using a different set of mechanical and electrical means to arm and initiate a fuze, U.S. Pat. No. 4,827,846 relates to an initiating device for a training round. The ""846 device uses a mechanical plunger triggered during the flight to arm a mortar training round.
The present invention includes an electronic safe and arm apparatus that stores electrical energy in a capacitor and delivers this energy at a desired time for initiating a semiconductor bridge initiator. The safe and arm electronic apparatus of the invention is small enough and strong enough to be located inside of the fin or body section of a tank projectile so that it may be used in a tactical, training, or test application. The safe and arm circuit uses a commercially available micromachined microeletromechanical systems (MEMS) accelerometer.
The MEMS accelerometer reacts to its environment mechanically by the movement of a proof mass that converts displacement information into electrical voltages. The electrical voltages are compared by the circuit to a fixed threshold voltage to safely arm the apparatus. Once armed, the apparatus delivers stored energy to an initiator for starting a pyrotechnic, propellant, explosive; or similar combustible train at a pre-set time determined by the user.
The invention is a novel and different way to create a safe and arm apparatus using off-the-shelf commercial products that have been ruggedized to withstand very harsh launch environments, such as tank launch shock and acceleration. At the heart of the apparatus is a solid state micromachined accelerometer and timing circuit. There are safeties built into the apparatus so that the capacitor will not charge until launch and spin environments unique to projectiles are experienced.
Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the following drawing.